(a) Field of the Invention
The present invention is related to a permanent magnet motor, and more particularly, to one that lowers high harmonic composition contained in start power wave form by reducing change of flux vector so to sufficiently upgrade its performance efficiency.
(b) Description of the Prior Art
Motor is a popular source of motive force in the manufacturing industry today where supply of motive force is needed to drive machines to execute rotation or other forms of motion. Whereas the motor is capable of converting electric power or magnetic power into mechanical power, it has become a must and is comprehensively applied in various types of industrial, electric appliance, and transportation system installations.
Motors are generally available in DC, AC, brush, and brushless. A motor is essentially comprised of a rotor and a stator. Distribution of magnetic flux promotes the rotor to engaging in rotary motion, which is then transferred into mechanical energy as needed. Wherein, a permanent magnet motor takes advantage of magnetism inherited in a magnet to provide magnetic flux. Value of the permanent magnet motor is highly appreciated in the market due to that it produces greater torque, efficacy and precision within a limited volume.
Referring to FIG. 1 for a schematic view showing a construction of a permanent magnet motor 10 of the prior art, the permanent magnet motor 10 includes a rotor 11 and a stator 12. The rotor 11 is disposed with multiple magnets 111 and the stator 12 indicates a ring structure. Multiple stator magnetic poles 121 are disposed an inner circumference of the stator 12, and each stator magnetic pole 121 may be wrapped up with a coil. An air gap is merely created between the rotor 11 and the stator 12 when the rotor 11 and the stator are inserted to each other. As the coils are conducted through, those stator magnetic poles 121 each made of permeable material interact among one another by means of a magnet 111 of the rotor 11 to produce an orbiting. A spindle 13 may be separately provided to the rotor 11 so to transfer mechanical energy for further use when the rotor 11 is engaging in orbiting.
As illustrated in FIG. 1, the rotor 11 of a four-pole motor is disposed with four rotor magnetic poles 112 with each provided with an arc surface 113. A distance between the arc surface 113 and a center 01 of the rotor 11 is gradually reducing from a central point 113a to both sides 113b, 113c; and a trough 114 is provided between two abutted arc surfaces while the gap between the trough 114 and the stator magnetic pole 121 is enlarged. Accordingly, flux of the stator magnetic pole 121a at where in relation to vicinity of the central point 113a of the arc surface 113 will be collected (Flux A) so that magnetism can be easily saturated. Meanwhile, another flux (Flux B) passing through the stator magnetic poles 121b and 121c will be reduced to lower a start power induced at where the stator coil is located. Given with the situation, number of windings of the stator coil must be increased so to provide higher start power induced at where the stator coil is located; however, the stator coil will cause more copper loss to fail effectively upgrade performance efficiency of the motor.